Electronic location monitoring and tracking of individuals or objects can be carried out in a number of ways. Determining the location of the tag can be provided using well-known techniques, such as GPS, cellular triangulation, or a combination of both. Further, in certain system applications, tamper detection capability and the ability to generate alarms upon detecting tampering or upon other conditions may be included. There are variants of electronic location monitoring and tracking systems. For example, some systems rely upon electronic monitoring at a fixed location such as the individual's home or place of employment. These systems can rely upon a land line telephone link and are commonly known as house arrest systems. These systems utilize a transmitter worn by the individual and a stationary receiver located at the monitoring location. When the individual is an “offender”, i.e., a person under a government-supervised program, the transmitter incorporates tamper-detection capabilities and upon such detection may transmit an alarm. The worn transmitter transmits a signal a short distance to the receiver located at the monitoring location. The receiver communicates with a central monitoring service over standard telephone lines. The tracking system of this type is limited in that it can only provide an indication of the presence or absence of the individual at the monitored location at a given time. This type of system cannot offer location information if the individual leaves the monitored location.
U.S. Pat. Nos. 5,867,103 and 6,160,481, which are incorporated by reference herein, disclose a system which provides for a locational tracking of a plurality of monitored persons. The system has a portable monitoring device for each of the monitored persons. Each portable monitoring device has means to secure the device to a respective monitored person and may include means to detect tampering with the secured device for offender applications. Additionally, each portable monitoring device has means to receive a distinct signal generated by a detached sending unit. Each portable monitoring device also has means to transmit a signal containing data. The system further has means to acquire the signal containing data transmitted by each respective portable monitoring device. The system has means to determine a positional location of the portable monitoring device based, at least in part, upon the distinct signal received by the portable monitoring device. The system has means to mark, at least within a range of time references, when the positional location reference was determined in the form of an occurrence reference. The system has means to store, for archival retention within a locational tracking database, at least a series of the position references and associative occurrence references of each portable monitoring devices of the tracking system.
U.S. Pat. No. 6,774,797, which is incorporated by reference herein, discloses a one-piece lightweight waterproof personal tracking tag which is attached to an individual using either a tamper detection strap or other suitable means of connection. The tag communicates with a global positioning satellite network and a wireless network to obtain geographic location information and to exchange data with a centralized data system. The tag monitors the location of the wearer of the tag, compares the monitored location to a database of acceptable and unacceptable location and time parameters and provides updates to a centralized database system, the monitoring station, and receives downloads and updates from the system.
For locational tracking and monitoring of one or more individuals, each having an individual set of allowed geographic and temporal restrictions, the system must maintain an extensive database of individuals and corresponding restrictions. In such applications, the tag preferably incorporates a microcontroller, flash memory, a cellular modem, a GPS receiver, tamper detection, and a rechargeable battery in a single lightweight unit. One or more individuals are provided with a tracking tag. Each of the tags reports into the monitoring station on a periodic basis. The reporting basis can be on a predetermined schedule and/or can be based upon detection of a violation or other reportable condition detected by the tag itself. Information reporting by the various tags is recorded and analyzed at the monitoring station by the data tracking system to determine if individual violations have occurred. The centralized data tracking system can then take an appropriate action to notify, respond to and/or correct the noted violation.
The tag's ability to properly function is limited by the capabilities of the tag's battery and the ability of the tag's circuitry to function properly in different locations. Current GPS based tracking systems, for example, will not function properly when GPS reception becomes impaired or is lost. In addition, the demands of system applications place increasing power loads and operating time requirements on the tag's batteries. Both of these shortcomings can be especially acute in offender tracking and monitoring applications where loss of offender locational monitoring is unacceptable. It would be desirable to provide a mechanism for efficiently extending the range of such GPS tracking systems particularly in areas in which GPS reception is impaired. It would also be desirable to provide such extended coverage where no action is required by the offender. It would also be desirable to provide such expanded coverage where removal of the offender's GPS device is not required.